The invention relates to the field of optics and more particularly to wide angle display apparatus and systems for visual projected displays up to and including 360.degree. displays.
In many training situations the presentation of an external environment is a necessity in order for the trainee to perceive visual cues and thereby learn to take actions or manipulate equipment to maximum advantage for a given situation. A particularly useful approach to reality in display is to produce an extremely wide-angle presentation to produce the effect of the observer being in the center of the scene activity. Such systems may approach and may also include 360.degree. panoramic projection. One prior attempt at 360.degree. image transfer in the taking or projection of an image has been to use a convex mirror to gather or project the 360.degree. scene in association with a viewing piece or film. In one example, a 360.degree. horizontal field is reflected from the surface of a strongly convex mirror, through a camera lens and onto a plane. The resulting picture has the camera lens at the center of the photograph and a distorted horizon in a circle around it. The distortions are unavoidable with this type of imagery because of simple laws of geometry. A hyperhemispherical space of the kind considered cannot be imaged on a plane without distortions.
If this distorted picture is projected back through the same optical system and onto a spherical screen, no distortions will be perceived by an observer provided (1) both the camera and the projection optics have the same distortion features and (2) the observer's eyes coincide with the exit pupil of the projection lens. However, it is normally not possible for the observer's eyes to coincide exactly with the exit pupil, but a reasonable tolerance (about one-fifth of the radius of the spherical screen) is acceptable. A further disadvantage of prior efforts at annular projection has been shadow interference caused by the light source means or by the observer, or both.